This invention relates to color light-sensitive materials, as well as an image processing method and apparatus using the same. More particularly, the invention relates to color light-sensitive materials capable of faithful color reproduction, as well as an image processing method and apparatus for performing color transformation on images produced with the color light-sensitive materials.
The level of color reproduction that can be accomplished by currently available light-sensitive materials is very high but by no means completely satisfactory. To cope with this situation, two approaches have been attempted.
One approach is by providing a fourth light-sensitive layer (cyan light-sensitive layer) to improve the precision in color reproduction as attempted in REALA, a color light-sensitive material manufactured by the Applicant, Fuji Photo Film Co., Ltd. As disclosed in JP 11-305396 A, REALA has a cyan light-sensitive layer provided as a fourth light-sensitive layer in addition to the ordinary red, green and blue light-sensitive layers, and a DIR compound which releases a development inhibitor during development is contained in order to enhance the interlayer development-inhibiting effects (so-called interimage effects), thereby improving the precision in color reproduction. This approach has successfully attained the intended object, improvement in color reproduction. On the other hand, the limitations from chemical reactions have prevented the fourth light-sensitive layer from exhibiting its performance to the fullest extent.
The other approach is based on introducing the digital image processing technology which has seen marked advances in recent years. A known version of this approach comprises forming images on a color negative film, photoelectrically reading the images with a scanner or the like so that they are converted to electric signals, subjecting the electric signals to image processing to prepare digital image data, and transferring image information to another image recording material using the digital image data. In this method, the information recorded on a taking color film is first converted to digital image data before image reproduction and the image containing the information is not directly projected onto a color paper through optics for preparing a finished color print. As a result, the constraint on film design, or the need to ensure that the blue, green or red color information in the subject corresponds to the yellow, magenta or cyan dye image information, respectively, is not necessarily a factor of paramount importance. This provides room for making a color light-sensitive material of higher capabilities by designing a different structure than the conventional color light-sensitive materials.
For example, JP 6-139323 A describes a color negative film that has a simple structure and which can yet output the image of a subject with faithfully reproduced colors, as well as a digital image processing method and apparatus using the color negative film. With this technology, the film structure can be simplified and an image faithfully reproducing the colors of the subject can be reproduced by digital image processing. However, the precision in color reproduction is inevitably limited by the potentials of the light-sensitive material used.
JP 2000-310840 A describes a light-sensitive material having a luminance layer in addition to the ordinary red, green and blue light-sensitive layers, as well as a method of forming an image from image data obtained by reading the light-sensitive material with a scanner.
However, the luminance layer which is primarily intended to obtain luminance information of high S/N ratio has sensitivity over a broad wavelength range and its spectral sensitivity has an increased overlap with those of other layers. This means that the information from the luminance layer has high correlation with the information from other layers and the addition of the luminance layer has not proved very much effective in improving color reproduction. In short, with the technology under consideration, one can expect an improvement in the reproduction of luminance but not in the reproduction of hues and saturation.
The present invention has been accomplished under these circumstances and has as an object providing a color light-sensitive material that integrates the two prior art approaches described above, which allows the fourth and ensuing light-sensitive layers to exhibit their performance to the fullest extent without suffering the constraint of chemical reactions and which makes it possible to achieve a color reproduction which is sufficiently improved by increasing the precision in color reproduction without being limited by the potentials of the light-sensitive material used.
Another object of the invention is to provide an image processing method using such improved color light-sensitive material.
A further object of the invention is to provide an image processing apparatus using the color light-sensitive material.
In order to attain the object described above, the first aspect of the present invention provides a color light-sensitive material having at least four light-sensitive layers of different spectral sensitivity waveforms in a visible range, with a covariance between spectral sensitivities of at least four light-sensitive layers being no more than 0.5, and at least four light-sensitive layers, after development processing, being colored with color materials having different spectral absorption waveforms.
Preferably, the spectral absorption waveforms of the color materials have peak wavelengths that differ from one another by at least 20 nm.
Preferably, at least one of the color materials has a spectral absorption maximum at a wavelength longer than 720 nm or shorter than 430 nm.
Preferably, at least four light-sensitive layers include a cyan sensitive layer.
Preferably, the cyan sensitive layer has a spectral sensitivity peak in a wavelength range of 470 nm-550 nm.
Preferably, at least four light-sensitive layers include a red-sensitive layer, a green-sensitive layer and a blue-sensitive layer.
In order to attain the other object described above, the second aspect of the present invention provides an image processing method comprising steps of exposing and developing the color light-sensitive material described above to form an image, allowing the image formed on the color light-sensitive material to be entered by an image input device having at least four light-sensitive portions of different spectral sensitivity waveforms and performing color transformation on an input image obtained by entering.
Preferably, the color transformation is performed on a basis of spectral sensitivity waveforms of the color light-sensitive material.
In order to attain the further object described above, the third aspect of the present invention provides an image processing apparatus comprising an image input device by which an image formed as a result of exposing and developing the color light-sensitive material described above is entered by at least four light-sensitive portions of different spectral sensitivity waveforms and an image converting unit for performing color transformation on an input image obtained by the image input device.
It is preferable that the image processing apparatus further includes a unit for entering spectral sensitivities of the color light-sensitive material and wherein the image converting unit is operated on a basis of spectral sensitivity waveforms of the color light-sensitive material as entered by the spectral sensitivity input unit.